1. Field of the Invention
The present invention relates to a power device with trenched gate structure and a method of fabricating the same, and more particularly to a structure which can increase the current density of the power device and the method of fabricating the same.
2. Description of the Prior Art
In recent years, the power source apparatus used in the field of the power electronics is required to be miniaturized and to exhibit a high performance. Therefore, in the power semiconductor element, vigorous efforts are being made in an attempt to improve the performance of the power source apparatus in respect of the improvements in the breakdown voltage.
Particularly, a power IBGT (Insulated Gate Bipolar Transistor) excellent in the breakdown voltage and in the adaptability for the large current is provided. The power IGBT is an element that is driven by a MOS gate. Widely known to the art there are two kinds of the power IGBT, i.e., a power IGBT of a planar structure, in which a MOS gate is formed in the shape of a flat plate, and a power IGBT of a trench structure, in which the MOS gate is buried inside a trench. Currently, a power IGBT of a trench structure has become a focus of attention because its structure makes it easy to obtain low on-resistance characteristics.
The power IGBT is a bipolar junction transistor (BJT) driven by an n-Metal-Insulation-Semiconductor Field Effect Transistor (n-MISFET), wherein the emitter and collector of the bipolar transistor constitute the emitter and collector of the IGBT, respectively, and the base current of bipolar transistor is the drain current of n-MISFET which is controlled by the gate electrode.
However, in order to get better performance of the power IGBT, there is still a need for increasing the current density of the power IGBT.